Thermally-controlled circuit interrupter



IN V EN TOR.

E. R..sToEKLE THERMALLY CONTROLLED lCIRCUIT INTERRUPTER Filed May 9. 1921 Mui/n Kiwa/kw April 1 ,1924.

BYv

rza.

aaah/1 ATTORNEY Patented Apr. l, 1924.

UNITED STATES PATENT OFFICE.

. ERWIN R. STOEKLE, OF MILWAUKEE, WISCONSIN, ASSIG-'NOR T0' THE CUTLER-HAM.-

MER-MFG. C0., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

-THERMALLY-CONTROLLED CIRCUIT INTERBUPTER.

Application led Kay 9, 1921. Serial No. 468,158.

To all whom it may concern Be it known that I, ERWIN R. STOEKLE, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Improvements in Thermally-Controlled Circuit Interrupters, of which the following is a full, clear, concise, and exact description, reference being companying drawing, forming a part of this specification.

This invention relates to thermally controlled circuit interrupters and more particularly to those of the fluid contact t pe.

In the construction of such control ers, great difficulty has heretofore been experienced in providing for positive automatic resetting thereof, due chiefly to the fact that the fluid contacting med1um tends very strongly upon reflux thereof to entrap one or more bubbles of air or the like which prevent such reestablishment of electrical continuity. Moreover, such difficulty is not materially reduced by subjecting the fluid tq increased pressure as by a piston or the li ce.

In my copending application, Serialvf No. 358,601, filed Feb. 14, 1920, are disclosed certain improved types of circuit interrupter of the general character aforestated wherein the foregoing and other difficulties are avoided by locating the fluid contacting medium preferably in an evacuated space, whereby obviously no gaseous medium is so entrapped and the present invention has amon its objects that of providing a cir.- cuit 1nterrupter of the same general type v but wherein the yaforementioned difficulties are obviated without requiring evacuation of the re ion about the contacting medium.

A furt er object is that of providing an exceedingl simple, rugged and rehable structure fbr the foregoing purposes which may be adapted to control currents of prac- 5 tically any desired magnitude.

Another .object is that of providing such a circuit interrupter adapted to control either alternating or direct currents of relatively high magmtude without material arcso ing. t

Other object and advantages will hereinafter appear. In the accompanying drawing wherein are illustrated certain of the embodiments which the invention may assume in practice,

had to the ac.

Fig. 1 is a longitudinal sectional view thereof, certain typical circuit connections therefor being illustrated diagrammatically; while,

Figs. 2 and 3 are similar views illustrating slightly modified forms of circuit interrupter.

In the construction illustrated in F 1, a constricted tube 5 of glass or other insulating material is provided terminally with solid electrodes 6 and 7 of any preferred type normally electrically connected by a quantity 8 of a liquid'conductive rnedium such for example as mercury. A conventional form of heating element which may comprise a resistive coil 9 is arranged about or adjacent to an intermediate portion of said tube as illustrated, whereby upon heating of such element as by a passage therethrough ofcurrent above a predetermined value, the mercury within the adjacent portion of the tube is adapted to become suddenly vaporized. Thereupon the liquid mercury above such vaporized portion thereof is suddenly expelled upwardly thereby interrupting electrical continuity of the column of mercury and interrupting circuit between the solid electrodes.

Thetube 5 is preferably arranged in a vertical position as shown whereby following escape or condensation of the vaporized mercury the displaced body of liquid mercury is adapted to flow back within the tube thereby automatically re-establishing the interrupted circuit. v y More specifically the electrode 7 is preferably secured within the lower end of the tube 5 by means of a liquid tight seal,I whereas a conductive cap 10 is preferably cemented or otherwise secured to and' outwardly of the lower portion of the tube asv shown to provide a terminal for said electrode. The upper end of said tube is preferably flared somewhat, as illustrated, whereas a relatively enlarged cap 11 which may be Iof conductive material is similarly cemented to and labout said flared up,-k

r end of said tube to make therewith also a liquid tight joint. The space within said cap above said tube is preferably of such capacity las to contain the entire body of mercury normally located within said tube.

The upper electrode 6 is permanently and electricallyconnected to the cap 11 by welding, soldering or in any other desired or lll preferred manner. Also if desired, a further cap member 12 composed of brass or the like may be spun about the upper portion of the inner cap as illustrated to provide a good electrical contacting surface for terminal connection of'the electrode 6.

The inner diameter Vof the tube is relatively large throughout the major portion of its length, the enclosed column of mervection, and also preventing free boiling of the heated mercury. That portion of the mercury column which is subjected to direct action of the heater 9 is furthermore maintained under a very considerable hydrostatic head due to the weight of the column of mercury thereabove plus the atmospheric pressure acting upon the top of said column. Thus a material degree of superheating of the mercury is required to eect vaporization thereof, whereas when vaporization once occurs said hydrostatic head is very rapidly reduced due to expulsion of mercury from the tube and into the enlarged cavity within the cap 11. Thus in turn the pressure upon the vaporized mercury is materially reducedwith consequent increase in rate of expansion of the vapor whereby as a final result that portion of the mercury column adjacent the heater is blown upwardly out of the tube or at least above the constriction thereof, thus effecting a sudden and wide separation of adjacent conductive surfaces Afor interruptionl of circuit therebetween and extinguishment of'any arc drawn incident to such circuit interruption.

Following condensation of the vaporized mercury or escapethereof from the interior of the tube the liquid mercury suspended within the cap 11 1s adapted to flow back under the force of gravity and reunite with the unexpelled portion of mercury located below the heater thereby re-establishing electrical continuity of "the interrupter and if during such reflux of liquidl mercury an air bubble should be entrapped within the tube, the constriction of the passage within said tube inherently prevents passage of any` bubble of such size as to impair conductivity of the column, therebelow or beyond, whereas the electrode 6 is extended through and beyond said constriction for electrical contact with the mercury therebelow, whereby the positiveness of the resetting action aforedescribed is in no wise affected by the presence of any bubble which may be entrapped. Said constriction also serves to retard reflux ofthe liquid mercury, thereby delaying the aforedescribed resetting action to afford a time element within which the switch con` trolled by the cutout device is adapted to function.

t With the circuit connections illustrated the heating coil 9 is connected in series with the load device 14 to be protected, a suitable electro-responsive switch 15 being arranged to control continuity of such joint circuit whereas the aforedescribed interrupter is arranged to control energization of the closing coil of Said switch whereby obviously upon rise, above a pre-determined value, of the current taken by the load device the circuit interrupter is adapted to act in the manner aforedescribed to effect opening of the switch 15 and de-energization of such joint circuit. The interrupter is thereafter adapted to reset automatically whereupon the main switch may be reclosed by momentary actuation of the push button 16.

The aforedescribed circuit interrupter is adapted to control alternating currents of relatively high magnitude and also to control direct currents of considerably less magnitude whereas where direct currents of greater magnitude are to be controlled the form vof the invention illustrated in Figs. 2 and 3 is preferable.

In Fig. 2 the general construction and arrangement is similar to that aforedescribed, the tube 5 being un-constricted internally. The passage within said tube is, however, constricted as in the preceding construction. Thus an enlarged electrode 6* of iron or other suitable conductive material is mechanically and electrically connected with the cap 11 by means of a wire 17 or the like,

lsaid electrode being in general cylindrical in form and of a size to fill the tube 5. Said electrode, however, is flattened upon one side as indicated at 18, thus affording the aforedescribed constricted passage connecting the portions of the interior of the tube located respectively above and below said electrode.

A corresponding electrode 7* also composed of iron or the like and of cylindrical shape and of a diameter such as to fill the interior of the tube is located at the bottom of said tube as illustrated and is electrically connected with the lower terminal cap thereof. Said electrode is in practice of such length that the up er end thereof is located adjacent the middle of the heating element I9 and materially s aced from the adjacent terminal portion o the electrode 6, the intervening space being normally filled with mercury which also extends through the constricted passage aforementioned and f within the upper portion of the tube in proximity to the cap 11,

The ope-ration of this form of the device is precisel similar to that aforedescribed, whereas tie special construction and arrangement of electrodes adapts the Same to the control of direct currentsof relatively high magnitude without material arcing.

Such capability of the device is dependent upon the fact that except under relatively high potentials an arc cannot be maintained between a solidl cathode and a mercury or other fluid anode. Thus upon sudden expulsion of the mercury between electrodes 7 and 6, such as occurs upon normal functioning of the device, the circuit between said electrodes is suddenly interrupted without arcing and irrespective of polarity sirlrc both of the contiguous electrodes are so 1 The upper end of the electrode 7 is preferably rounded or convexed, as shown, to promote complete expulsion of the liquid mercury located thereabove, since any portion which is not at once expelled is caused to travel outwardly of the tube and nearer to the heater and hence becomes vaporized immediately.

The construction illustrated in Fig. 3 is in al1 material respects similar to that of Fig. 2 except for the construction of the electrode 6b which as illustrated is in the form of an axially elongated annulus of exterior diameter suflicient to fill the interior of the tube completely, the opening 19 in said annulus constituting the aforedescribed constricted passage forthe mercury column.

The two latter described figures obviously ssess all the aforedescribed advantages of gig. 1 in that the upper electrode extends below the constriction in the mercury column and thus insures re-establishment of electrical continuity through the interrupter irrespective of possible trapping of air bubbles of appreciable magnitude above the constriction, whereas any relatively small bubbles which might be carried beyond the constriction will in any of the aforementioned instances be expelled upon heating of the column before the temperature of response of the device is attained.

Also in each of the constructionsaforedescribed the interruption of circuit occurs in an atmosphere of Amercury vapor only, no atmospheric oxygen or other deleterious gaseous agency being present, whereby deterioration of the mercury due to contamination by the prese-nce of such agents during arcing is entirely prevented.

It is of course to be understood that the constructions illustrated in Figs. 2 and 3 are `adapted to control alterating as well as direct currents. Also it should be noted that the space within the cap 11 while preferably sealed against the escape of liquid mercury therefrom is nevertheless preferably in such communication with the outer air as to render the pressure within said space and upon the column of mercury within -the tube at all times substantially atmospheric pressure.

What I claim as new and desire to secure by Letters Patent is:

1. A thermally controlled circuit interrupter comprising a container having a depending tubular extension to contain a column of conductive fluid which is liquid at working temperatures, electrodes to be connected by said fluid, means restricting the cross sectional area' of said column beyond the portions of said electrodes to be so connected and thermal means for subjecting said column of' fluid to fluid pressure of its own vapor to force fluid from between said electrodes and past the constriction of said column for interrupting circuit between fluid surfaces intermediate said electrodes.

2. A thermally controlled circuit interrupter comprising a container having a depending tubular extension to contain a column of conductive liquid, electrodes to be connected by said liquid and means exterior to said container to subject said column of liquid to fluid pressure of its own vapor for interrupting such connection between liquid surf-aces, said column having means associated therewith beyond the region of such circuit interruption to prevent free boiling of the liquid under the action of said thermic means to thereby provide for effecting such interruption suddenly.

3. A thermally controlled circuit interrupter comprising a substantially vertical column of conductive liquid, a support therefor having a. reservoir located above said column land in communication therewith, said column having associated means effecting constriction thereof adjacent said reservoir, electrodes having parts to be connected by an unconstricted portion of said column and thermic means to act upon such portion of the column for subjecting the latter to fluid pressure of its own vapor, said constriction serving to prevent free circulation or boiling of the liquid under Ithe action ofl said thermic means to thereby provide for sudden ejection of a portion of said column from between said electrodes and within said reservoir for interruption of circuit between said electrodes.

4. A thermally controlled circuit interru ter comprising a substantially vertical co umn of conductive liquid of relatively large cross sectional area having therein a constriction, electrodes to be connected by said liquid upon one side of said constriction, a support for said column having a relatively enlarged reservoir located upon the opposite side of said constriction and above said column in open communication therewith and thermic means for effecting vaporizati'onof such liquid adjacent said elecs trodes for forcing the liquid above the region ct vaporization upwardly beyond said constriction and withinsa-id reservoir, the cross sectional area of said column being suicient to permit automatic reflux of said liquid followin escape or condensation of the vaporized liquid, subject to delay by said constriction.

5. A thermally controlled circuit interrupter comprising a substantially vertical column of conductive liquid of relatively large cross sectional area having therein a contriction, electrodes to be connected by said liquid upon one side of said constriction, a support for said column having a relatively enlarged reservoir located upon the opposite side of said constriction and above said column in open communication therewith and thermic means for effecting vaporzation of such liquid adjacent said electrodes for forcing the li uid above the region of vaporization upwar ly beyond said constriction and within said reservoir, the cross sectional area of said column being sufficient to permit automatic reflux ot said liquid following escape or condensation of 'the vaporized liquid, subject to delay by said constriction, said constriction serving to prevent entrapment between said electrodes of any gas bubbles of size suilicient to prevent rea-establishment of electrical connection therebetween.

6. thermally controlled circuit interrupter comprising an elongated tube of insulating material to contain a column ot mercury, means restricting the cross sectional area of said column, electrodes to'be connected by said column and provided with vterminals located exteriorly of said tube, certain of said electrodes being arranged toY shunt said restricted area of said column and thermic means associated with said column to effect sudden vaporization of a portion thereoiE adjacent said electrodes for upward expulsion of the mercury located therebetween to 4thereby provide for sudden interruption of circuit through said electrodes.

7. A thermally controlled circuit interrupter comprising an elongated tube of insulating materia to contain a column of conductive liquid, means associated with said turbe to provide a reservoir thereabove and in open communication therewith, means restricting the cross sectional area 0f said column at a region adjacent said reservoir, electrodes to be connected by said liquid and provided with terminals located eXteriorly of said tube, certain of said electrodes being arranged to shunt said restricted area of said column and thermic means associated with said column to effect sudden vaporization of a portion thereof located between said electrodes for expulsion of liquid located therebetween upwardly and within said reservoir to thereby rovide for sudden interruption of circuit etween said electrodes.

8. A thermally controlled circuit interrupter comprisin an elongated tube of insulating materia to contain a column of conductive liquid, means associated with said tube to provide a reservoir thereabove and in open communication therewith, means restricting the cross sectional area of said column at a. region adjacent said reservoir, electrodes to.be connected by said liquid and provided with terminals located exteriorly of said tube, certain of said electrodes being arranged to penetrate said restricted area ot' said column and thermic means associated with said column to provide for sudden vaporization of liquid between said electrodes for effecting expulsion of all the liquid between said electrodes to thereby interrupt circuit substantially without arcing.

In witness whereof, I have hereunto subscribed my name.

ERWIN R. STOEKLE. 

